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Instruments Used for Measurement
Types of Sound Pressure Level (SPL)
Meter
Type 0 Vary accurate. Used as lab reference std. High std of
tolerance over wide freq range. Not used “in the field”
Type 1 In labs or the field, high precision
Type 2 General Field meter
Type 3 Basic level indicator. Shows if exceeded levels. Least
accurate.
Element B6 / 3
Instruments Used for Measurement
Types of Sound Pressure Level (SPL)
Meter
Noise surveys – should use at least type 2
Readings at A weighted L Aeq
C weighted max peak SP to above 140 dB(C)
Ear protection and control assessments
Octave band anaylsis feature with above
Element B6 / 3
Methodology
SPL (La)
A weighted intensity of sound at given moment and
position
Equivalent cont. SPL (L Aeq)
Avg measure over reference period
dB(A)
Peak Pressure Level
CNWR exposure limit 140dB(C)
Element B6 / 3
Methodology
Ideally
Take readings at persons ear
Most work situations –
Personal portable device
Element B6 / 3
Terminology
L EP,d
Daily personal noise exp level
LAeq
Equivalent A weighted continuous sound level
LA
A weighted SPL, dB(A)
LC
As above, dB(C)
L WA
A weighted Sound POWER level, dB(A)
Octave band
Band of freq, Hz
Element B6 / 3
LEP,d
True average level over 8 hrs
Taken from LAeq
Use HSE Ready Reckoner Calc Table
Different levels throughout shift
Prioritise higher level tasks / highest exp points (HSE)
Element B6 / 3
L AEQ
Noise which varies with time
A weighted average
To maintain L AEQ when SPL x 2 (
+3dB)
Exposure time must be halved
Element B6 / 3
Frequency Analysis
Noise source measured at freq bands
Octave band = highest freq is twice
lowest freq
Band denoted by centre freq. (i.e. 1kHz)
Measure in all bands to match noise
source to personal hearing protection
Element B6 / 3
Background Noise
Any sound other than that being measured
Heating, vent, aircon, other equip, traffic etc.
Measuring :
Background noise must be at least 3 dB less than source
Correction level
Measure level with source running
Measure background noise with source off
Calc diff. if less than 3 dB then too high for acc. Measurement
If between 3 and 10 dB then correction
If greater than 10 dB then no correction
Element B6 / 3